# Math Help - Rotation of Axes to graph a quadratic equation with a xy term

1. ## Rotation of Axes to graph a quadratic equation with a xy term

I need to graph:

(x^2)+3xy+(y^2)=1

but, using the cot(2theta)=(a-c)/b

I got 0, and using

cot = 0degrees

or

cot = 90degrees

does not remove the xy term.

2. Originally Posted by mathmana
I need to graph:

(x^2)+3xy+(y^2)=1

but, using the cot(2theta)=(a-c)/b

I got 0, and using

cot = 0degrees

or

cot = 90degrees

does not remove the xy term.

$\cot (2 \theta) = 0 \Rightarrow 2 \theta = 90^0 \Rightarrow \theta = 45^0$.